The present invention relates generally to visual media soft lighting systems such as visual media display illumination and studio and location illumination for television, video, theatrical, film, and photographic production.
In visual media illumination or lighting, soft light refers to diffused light that tends to “wrap” around objects, casting virtually no visible shadows or diffused shadows with soft edges. Visual media lighting can emphasize important details or obscure them. It can flatter a subject by bringing out positive attributes and it can de-emphasize or hide less attractive attributes. The use of soft light is especially popular in cinematography and film-making to cast “shadowless light” that reduces shadows without creating additional shadows, to make a subject appear more beautiful or youthful by making age lines and wrinkles less visible, and by supplementing the lighting from other sources. This technique is also used to perform motivated lighting in which light in the scene appears to come from actual light sources depicted in the scene. Soft light does not cast shadows that would be a giveaway of a supplementary light source.
Prior to the 1980's, studio and location filming used different methods to create a natural, shadowless soft light effect, which is sometimes called base light or fill light. The goal of soft lighting has been to bring a base light, or ambient light, to a dark space. Accent lighting was then added with key lights or back lights in accordance with standard three point lighting techniques. By using three point lighting, the filmed subject may be illuminated however desired while also controlling or eliminating the shading and shadows produced by direct lighting. The difference between the key light and the fill light in three point lighting is that key light is generally directional light and fill light is generally diffused light. The key light is meant to define the object/person, whereas the fill light is used to soften the shadows and even-out the contrast. In three point lighting the back light separates the object from the background, giving depth to the scene.
Light passing through a diffuser is softer and purposely less-defined and less-directional. A good example of natural diffused light is when the sun shines through fog. The light appears to come from all directions, whereas without the fog one would see distinct shadows produced by undiffused, direct sunlight. To achieve soft (i.e., diffused) base light artificially, large, bright incandescent lights are sometimes set up to shine through large translucent silks or to be reflected off shiny or flat, white boards. These methods, however, are clumsy to set up and control. In addition, they use a large footprint, require much manpower, time, and supporting equipment. Hot incandescent lights use significant amounts of power, and air-conditioning is often required to cool stages. Beginning in the 1980's, fluorescent lights were sometimes used, cutting power requirements, heat, footprint and weight. Currently, various combinations of such equipment are used.
Another aspect of visual media soft lighting is the color temperature of the light source. One consideration for professional cinematographers, using film, is how the color temperature of the illumination interacts with the film emulsion. (Video recording has white balance control and so is less sensitive to color temperature issues.) The Kelvin temperature scale (K) is the numerical measurement that is used to describe the color appearance of light produced by a light source (e.g., a lamp) and also the color appearance of the light source itself.
Color temperature values are based upon a theoretical black body radiator, such as a block of black metal through which electric current is passed. Black body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature, referred to as Planck spectrum or Planck's law. The spectrum is peaked at a characteristic frequency that shifts to higher frequencies with increasing temperature. As the block of black metal is heated, it turns red-yellow, then white, then blue. As the temperature of the metal is measured at any given color produced, the color is matched to that temperature and a color temperature value is determined. For example, a Kelvin temperature of 5000K produces roughly neutral light, whereas 3000K and 9000K produce light spectrums which shift from neutral to contain more orange and blue wavelengths, respectively.
The Kelvin temperature of light sources is thus used to categorize them as warm, neutral or cool sources. These terms are not directly related to temperature; instead, they describe how the light source appears visually. Warm sources actually have a lower color temperature (3500K or less), producing a red-yellow appearance associated with conventional tungsten filament incandescent bulbs (often referred to as “tungsten lighting”). Neutral sources (between 3500K and 4100K) tend to have a more yellow appearance. The following table is a rule of thumb guide to the correlated temperature of some common light sources:
Color TemperatureLight Source1000-2000 KCandlelight2500-3500 KTungsten Bulb (household variety)3000-4000 KSunrise/Sunset (clear sky)4000-5000 KFluorescent Lamps5000-5500 KElectronic Flash5000-6500 KDaylight with Clear Sky (sun overhead)6500-8000 KModerately Overcast Sky9000-10000 K Shade or Heavily Overcast Sky
A lamp with a color temperature of 5000K is considered pure white (full spectrum) light, with the lamp becoming more blue in color as the color temperature is increased. Warm light sources are traditionally used for applications where warm colors or earth tones dominate the environment, such as when there is a need to impart a feeling of comfort, coziness and relaxation. Cool light sources (5000K+) with high color rendering capabilities, such as full spectrum lights, are traditionally used for applications where there is a need to enhance all colors equally. Soft lighting for video is typically flat (no shadows) and has a high color temperature (approx. 5600 Kelvin). In contrast, typical stage soft lighting is more dimensional, casting shape-defining shadows, and lower in color temperature (approx. 3200 Kelvin). Soft lighting for cinematographic film purposes may use both types.
Currently, some visual media lighting employs LED lighting technology such as an array of front-facing LEDs distributed across a rear panel and directly illuminating a translucent diffuser. An LED luminaire generally consumes less power and generates less heat than corresponding incandescent and fluorescent soft lighting products and can typically cast light at greater effective distances. Moreover, typical life span ratings for an LED lamp can be as much as 100,000 hours. As a result of these advantages, LED luminaires have recently begun to be used in certain stage, studio and location lighting applications. However, these LED luminaires do not achieve color temperature and color rendering characteristics of conventional incandescent lights. Further, previous such LED luminaires have not been designed to work well in a range of different physical space requirements and changing set conditions with a minimum of set up time. Accordingly, although luminaires using LED technology have found some limited use in the arts, media, and entertainment soft lighting industry, there still exists a need for improvement in the light quality and efficiency in order to satisfy the lighting performance expectations of visual media lighting professionals.
Accordingly there presently exists a need to improve the quality, performance, portability, and footprint requirements of existing lighting equipment used to provide soft visual media light in stage, studio, and other visual media lighting applications. It would be a further advantage to provide soft lighting equipment that is reconfigurable and able to accommodate a range of different physical space requirements including relatively tight spaces, which is portable and which also is adaptable to changing set conditions with a minimum of set-up time. The various aspects of the systems of the subject invention as disclosed herein are particularly suited for meeting these and other constraints in this field.